Conventional print monitoring systems are commonly used to monitor printed matter in some types of paper/sheet handling systems and to make certain control decisions based upon the character of the printed matter. Print monitoring systems can detect the precision with which the printing system has formed the printed matter and/or the consistency with which the matter is printed across the paper. For example, in a laser printing system, the monitoring system detects low-toner situations where the contrast of the printed matter has degraded unacceptably.
The inclusion of explicit control information on the printed matter is many times unacceptable. Typical printed objects do not include machine readable information a predictable locations to enable the print monitoring system to ensure the quality of the overall print on the printed object.
Attempts have been made at placing non-intrusive information onto printed matter. Glyph codes are one example. Information is typically encoded into glyph codes by modulating the orientation of optically detectable symbols or glyphs. Using such techniques, large amount of information is encoded into printed images for copy control. Generally, however, glyph codes are not appropriate for print monitoring. The glyphs can be placed into images that may not be present on each printed object and that may not reside at the same location on each printed object. Therefore, conventional image capture devices that monitor for glyph-based symbols must process the entire area of the printed matter, increasing the expense in both the image capture device and the processing capability required in the print monitoring system.
Typical print monitoring systems are used for digit control and sequence control. Such systems do not provide a methodology for continually monitoring the print quality of each individual printed object and identifying errors in print quality. If the printed object is a game ticket in which a portion of the print is covered in a subsequent processing step, it is desired that any printing error be identified during the printing process so that the particular ticket or tickets can be specifically identified prior to being sent to the ticket distributors.